1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method of the semiconductor device.
2. Description of the Related Art
A BGA (Ball-Grid-Array) type semiconductor package has been known as a semiconductor package for a semiconductor device.
Such the semiconductor device comprise a lead frame, a semiconductor chip, bonding wires, and solder balls.
The semiconductor chip is mounted on one side of the lead frame with wire bonding which establishes electrical connection. The solder balls are disposed on an underside portion of the lead frame at predetermined intervals, and act as connection terminals of the semiconductor device. The semiconductor chip and the bonding wires are encapsulated with a plastic (resin).
The solder balls are melted when the semiconductor device is mounted on a printed circuit board, thus the solder balls are connected to the printed circuit board. As a result, electrical connection between the semiconductor chip and the printed circuit board is established.
Conventionally, there are two typical ways to form a region (land) of the lead frame on which the solder balls are disposed as follows.
1) Half Etching (disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H9-246427): To etch regions, which do not correspond to portions to be the lands, on one side of the lead frame to predetermined depth (do not etch fully) to form the land portions. Then the semiconductor chip is mounted on the other side of the lead frame with wire bonding. The mounted chip and the bonding wires are encapsulated with a plastic. The encapsulant plastic also covers the half-etched portions, thus the lands are exposed. Finally, the solder balls are formed on the lands.
2) Limited Encapsulation (disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H10-84055): To encapsulate the semiconductor device wholly except regions to be the lands. More precisely, after the chip is mounted on the lead frame, the semiconductor device is subjected to encapsulation process with using a mold which has projected portions corresponding to the regions to be the lands. The semiconductor package is wholly encapsulated except the land regions by injecting an encapsulant plastic. Thus, the lands are exposed, and the solder balls are formed on the lands.
According to the first method, the lead frame is weakened because of the half etching. Therefore, jamming tends to occur during the manufacturing process. As a result, this method costs much because yield of the semiconductor device is poor.
The second method also has disadvantages. The available minimum intervals among the projected portions may be 0.6 mm. Therefore, this method is not suitable for manufacturing a semiconductor package in which lands are formed at intervals equal to or less than 0.6 mm. Moreover, various molds are required in accordance with various sizes of the solder balls, land intervals, and the like. This method also costs much.